The Tech Lab: Alastair Reynolds

Science fiction author Alastair Reynolds, author of Revelation Space and Century Rain, wonders if we could do a better job of looking back into history.

If there's a silver lining to the dark cloud of CGI-dominated blockbusters that seem to infest the cinema lately, it's this: the same digital technology that can make Spiderman or Hulk leap around the screen in a singularly unconvincing fashion, can also be used to create something infinitely more interesting: the past.

Imagine if you could actually walk around in a simulated version of a scene from history? Wouldn't that be worth an hour of anyone's time?

I'm not talking about the Star Trek holodeck here. I'm talking about something we could have sometime next week, if the appropriate technologies were combined.

For a start, we'd need a computer system capable of running the simulation - but in these days of super-powerful games consoles, that surely isn't too much of an ask.

Imagine fast-forwarding through entire centuries, watching buildings rise and fall, the Great Fire of London coming and going in a convulsive flash, transforming half the city

We'd also need a display device, feeding a constantly moving three-dimensional viewpoint to the participant, something like a virtual reality headset. We'll call them goggles, but they don't have to look any weirder than Bono's last pair of wraparound shades. You don't want to look like a complete berk, do you? Actually, let's not go with Bono's shades.

The problem is, virtual reality is so Lawnmower Man, so 1990s. Can't we go one better than that? Can't we integrate the simulation with the real world instead?

Easily enough, as it happens. We certainly don't need any kind of motion capture suit or scanning rig, because that's not how it's going to work. The system isn't going to track how you move; it's only going to track the movement of the wraparound goggles.

With differential GPS receivers embedded in the goggles, that's all the data it needs.

You're not going to be trapped in some windowless room somewhere, prancing around like a demented mime artist. You're going to be walking through your favourite city, perhaps the place where you actually live. Simultaneously, the goggles are feeding you a one-to-one overlay derived from the computer simulation, integrated seamlessly with your view of the real world.

Wraparound shades might be all you need to see the past

The key is that the goggles don't have to feed you the view of the present day. They can feed you the past.

Imagine you're walking through London. There's a slider on the left side of the frame; you can reach up and adjust it as you walk. By moving the slider, you can dial all the way back to the Blitz, or the time of Samuel Pepys, or the Londinium of 45AD.

It would be a fascinating - not to mention disorientating - experience. Imagine fast-forwarding through entire centuries, watching buildings rise and fall, the Great Fire of London coming and going in a convulsive flash, transforming half the city. You'd feel like HG Well's time traveller, hurtling through time. You'd get an entirely new perspective on a familiar neighbourhood.

Of course, there'd need to be a certain amount of fudging. Streets and rivers re-align themselves; what was once passable becomes impassable. Ground levels change dramatically. But all of that could be accommodated; the aim would be to educate and illuminate, but that wouldn't mean that the simulation had to be rigorously correct at all times.

Speaking of education, it seems to me that one of the earliest applications of such a technology - if it doesn't already exist in embryonic form - would be in museums, especially those dealing with the buried past.

Imagine visiting an historical site a few years down the line, something like the Roman spa in the city of Bath. Instead of being given the option to hire a handset with a pre-recorded commentary, you get given a pair of goggles, with an associated earpiece.

They're a bit scuffed from repeated use, but they've been thoroughly cleaned since the last person used them. You put them on and move into the museum proper. The goggles are preset for 45AD, but you can move the left-hand slider up and down to surf through the ages. If you wish you can even skip to post Roman times and stroll around the greening ruins.

Reynolds: computer graphics could help us visualise the past

Importantly, there's a second slider on the right side of the goggles. This one is preset to low immersion: when you first don the goggles, it displays the simulated overlay as a ghostly tracery, a bit like the vector graphics of old arcade games. You can see where walls and floors used to be, but you're still firmly anchored to the real world.

Turn the slider up a bit, though, and the overlays become progressively more solid, more photo-real.

Turn it up a bit more and the glasses begin selectively deleting what they don't want you to see - the modern walls that are in the wrong place, the modern ceiling that should show the blue sky and clouds of Roman Britain instead. What's more, the slider goes even further up the scale.

There's no reason why the software can't drop in a few authentic-looking Roman citizens, going about their business. As you walk past them, your earpiece picks up snatches of murmured conversation in Latin. A subtitle tells you what they're really saying.

While you're at it, why not have the option of deleting some of your fellow visitors? You came to see Roman ruins, not a gaggle of exchange students ticking off another item on the itinerary.

Depending on the software, the goggles could overlay a "Roman" over each visitor, or render them entirely invisible until they came within a certain collision volume. At which point, they could be progressively de-erased, or perhaps flagged with a graphical outline. It would be up to you how far you adjusted the slider.

I don't know. I think this would be pretty fantastic, but who knows? Perhaps it would be yet another reason not to exercise the imagination; yet another reason not to have to think too hard.

After all, you have to think to make sense of schematic diagrams and dioramas, the usual stuff of museums. You have to work at it a bit. And maybe that's a good thing.

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